Interpretive Summary: Scientists from the Anadolu University in Turkey, King Saud and Al Kharj Universities in Saudi Arabia, the University of Mississippi and the Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS, in Gainesville, FL, report that oils and compounds from date palm, Phoenix dactylifera, were nearly as good Yellow Fever mosquito repellents as the well known commercial repellent DEET (N,N-diethyl-3-benzamide). Using analytical techniques such as Gas Chromatography/Flame Ionization Detection (GC/FID) and Gas Chromatography/Mass Spectrometery (GC/MS), characterized total of 16 compounds were identified and their relative amounts determined. These 16 compounds accounted for 99% of date palm fruit essential oil. The five major components of the oil were tested for repellency in laboratory bioassays. The best repellents were two of the main compounds: 3,4-Dimethoxytoluene and 2,4-dimethoxytoluene. These two major components are likely responsible for the repellent activity of data palm essential oil. The results of this research will be useful to other researchers performing research to discover new mosquito repellents as well as be of potential use to commercial companies developing new mosquito repellent products.

Technical Abstract:
Date palm, Phoenix dactylifera L. (Arecaceae), grows commonly in the Arabian Peninsula and is traditionally used to treat various diseases. The aim of the present study was to identify chemical composition of the essential oil and to investigate the repellent activity. The essential oil of P. dactylifera was obtained by hydrodistillation from the spathe, a specialized leaf structure that surrounds the pollinating organs of the palm. The oil was subsequently analyzed by GC-FID and GC-MS. The oil showed promising repellent activity against yellow fever mosquito - Aedes aegypti. Sixteen components were characterized, constituting 99% of the oil. The main components were 3,4-dimethoxytoluene (73.5%), 2,4-dimethoxytoluene (9.5%), '-caryophyllene (5.5%), p-cresyl methyl ether (3.8%), and caryophyllene oxide (2.4%). The minimum effective dosage (MED) for repellency for the P. dactylifera oil was 0.051mg/cm2, which had moderately lower potency compared to DEET (0.018 mg/cm2) in the “cloth patch assay”. The five major compounds were individually assayed for repellency to determine to what extent each is responsible for repellency from the oil. 3,4-Dimethoxytoluene and 2,4-dimethoxytoluene showed the best repellent activity with the same MED value of 0.063 mg/cm2, respectively. The results indicate that these two constituents which comprise a large proportion of the P. dactylifera oil (83%) are likely responsible for the observed repellent activity. In this aspect, the P. dactylifera spathe oil is sustainable promising new source of natural repellents.